Field of the Invention
The present invention relates generally to high speed data networks over hybrid fiber coaxial (HFC) cable plant.
Background Art
It is envisioned that in future cable networks the frequency spectrum for upstream communications will be expanded into higher frequency bands (e.g., over 1 GHz, but even extensions to 200 MHz are significant compared to current practice topping out at 42 MHz in North America and 65 MHz in Europe). As such, signal attenuation due to cable loss will become significant for upstream communication in the higher frequency bands, and will also cause signals at the headend to have widely varying signal strengths as signals will experience different cable attenuations depending generally on the length of cabling between the cable modem and the first upstream amplifier, the type(s) of cabling (traversed to the first amplifier), and the frequency bands over which the signals are transmitted.
Existing solutions typically deal with similar problems by having the cable modems use as much transmission power as needed to achieve a desired received signal strength at the headend, without regard to cable length (between the cable modem and first upstream amplifier) or cable type(s) or frequency assignment. Thus, conventional solutions are highly sub-optimal in terms of power utilization.
There is a need for frequency spectrum and modulation scheme allocation techniques that optimize power utilization and enable similar upstream transmission power by cable modems and signal-to-noise (SNR) ratio at the headend.
The present invention will be described with reference to the accompanying drawings. Generally, the drawing in which an element first appears is typically indicated by the leftmost digit(s) in the corresponding reference number.